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Hey all - My 15 year old son and I are working through the mechanics of my his first car, and I am looking for advice on the cooling system.

First:
1966 Coup, A-code, 289 4bbl with AC and power steering. The fan is a six blade, belt driven, 17" diameter, and it sits about 3" away from the 2-row original-looking radiator core.

We live in Phoenix, and since it is currently winter, it is 72 degrees and sunny. We picked up the car about a month ago. It had been sitting in a warehouse in CA for 40 years. Nonetheless, it runs and drives, but we are working through some of the bugs that need to be worked out. The one we are currently working on is that it is overheating. We so far have replaced the temp sending unit (it was completely dead), flushed the block and radiator, installed a 180 deg thermostat (it was missing), replaced the radiator cap (13lb), and replaced the supply, return, and bypass hoses. We spent considerable time trying to make sure we purged the air out of the system after the flush, but I will be honest, I am only about 80% sure we got it all.

When we start the car from cold, it will run and idle for about 15 minutes before the temp gauge goes to about center. As I watch with the radiator cap off, I can see some flowing coolant after a while, but then there is an event point where it just guysers out of the cap. Probably 4-6" of fountain coming out of the fill hole. If I leave the cap on, the gauge will float up to about 80% to H, and then start coming back down to about 60%, then swing up to 85%, back to 65%... it kind of ratchets its way up to the top end of the gauge and then I shut it down. At that point, coolant is streaming out of the pressure relief hose.

A couple of things I figured out by reading through many of the posts... first - it does not have a fan shroud, and that appears to be a pretty big deal. So I went ahead and ordered one that is close to stock.

Second - I learned that taking temps with the ol' IR gun could prove handy, so we will be doing that part tomorrow. I plan to take reads at the thermostat housing, supply hose and return hose. I am hoping to figure out whether or not the radiator is actually removing any heat. Then I will do it again with the fan shroud on to see if I have any improvement. I will also use this data to see if the sending unit/gauge is reading correctly.

So here are my questions:
1) is it normal to get a guyser out of the radiator?
2) Are there any other points that I should be reading temperature?
3) I am pretty suspicious of the radiator being plugged up after sitting for 40 years, so assuming I need to replace it, should I go with a 2, 3, or 4 row? Does anyone have a specific recommendation for a Phoenix based car?
4) Knowing it will be blazing hot in a few months, and the car has Air Conditioning, should I plan to install an electric fan?

Thanks in advance for your insight!
You for sure have an air pocket so that when the motor gets to running temp the stat opens lets all that cool coolant flow and here comes ole faithful I was a mechanic for 50 years and it happened to me in November in my 66. Your on the right track with an infared temp taker they are super for checking if yo have cold spots on your radiator IE blocked. Hope this helps John B
 

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1967 Mercury Cougar XR7
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Just invest in a new alu radiator, either OEM style or 1 row larger. Then you might want to replace the WP. You can get a hi flow version for that engine. Electric fan isn't necessary, a good flex fan will work just fine. If the mustang is an automatic I would get the radiator without the tranny cooler instead id recommend installing a separate trans cooler. Keep the radiator for engine cooling only. Just my thoughts.
Patbuch, I hate to disagree with you here, but you want LESS rows with an aluminum radiator than brass - not more. This is very important. Usually 3 core brass or 2 core aluminum is the most you want. Aluminum radiator tubes are stiffer, and can be made wider than the softer copper tubes in a brass radiator. That means a 2 core aluminum is about the same thickness as a 3 core brass radiator.
So why not add more rows? Two big reasons. The first one's simple. Fitment. They get too thick, and it's hard to get them in there with a fan and shroud, unless you want to customize your radiator support and go through a lot of fuss. The other very good reason is that with extra fins and thickness, air trying to get through has more resistance. It's hard to force enough airflow through it. Worse, slow-moving air picks up a ton of heat from the first cores. When it's saturated with heat, the last rows of fins do nothing to cool the radiator any more than the smaller thinner radiator that lets air through more easily.
Aluminum radiators work well, and are lighter than brass, but aluminum also tries to work as a sacrificial anode to convert rust back to iron. If your car's block has significant corrosion inside, you will need to be sure to change out your antifreeze frequently (it has anti-corrosion agents that will break down over time). Failure to do so will mean your nice new aluminum radiator starts to be eaten away from the inside out, and it will spring leaks as it tries to 'fix' your block.
Always use only distilled water in your cooling system (along with good quality antifreeze) Tap water greatly accelerates corrosion.

And lastly, if you have a choice, never use a flex fan. The blade design is not very efficient. They thrash air around and typically steal even more power than a fixed-blade fan, surprisingly. Using a thermal clutch fan with a 24" 'big block' radiator and shroud will cure all cooling problems for your car - if it even has cooling problems.

Correct timing, 192 degree stock thermostat, shroud, and proper cooling fan are all very important.

I'm sorry to 'pick on you', @[email protected] ! I appreciate you being a part of these forums, and don't want to feel like I'm smacking you down either. A lot of people get a lot of misinformation about radiators and cooling, and I see an awful lot of people spending big bucks on stuff that doesn't work well.

Best wishes, you guys.
 

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1966 Mustang A-Code Coup, 289 V8 Automatic transmission
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Discussion Starter · #23 ·
Patbuch, I hate to disagree with you here, but you want LESS rows with an aluminum radiator than brass - not more. This is very important. Usually 3 core brass or 2 core aluminum is the most you want. Aluminum radiator tubes are stiffer, and can be made wider than the softer copper tubes in a brass radiator. That means a 2 core aluminum is about the same thickness as a 3 core brass radiator.
So why not add more rows? Two big reasons. The first one's simple. Fitment. They get too thick, and it's hard to get them in there with a fan and shroud, unless you want to customize your radiator support and go through a lot of fuss. The other very good reason is that with extra fins and thickness, air trying to get through has more resistance. It's hard to force enough airflow through it. Worse, slow-moving air picks up a ton of heat from the first cores. When it's saturated with heat, the last rows of fins do nothing to cool the radiator any more than the smaller thinner radiator that lets air through more easily.
Aluminum radiators work well, and are lighter than brass, but aluminum also tries to work as a sacrificial anode to convert rust back to iron. If your car's block has significant corrosion inside, you will need to be sure to change out your antifreeze frequently (it has anti-corrosion agents that will break down over time). Failure to do so will mean your nice new aluminum radiator starts to be eaten away from the inside out, and it will spring leaks as it tries to 'fix' your block.
Always use only distilled water in your cooling system (along with good quality antifreeze) Tap water greatly accelerates corrosion.

And lastly, if you have a choice, never use a flex fan. The blade design is not very efficient. They thrash air around and typically steal even more power than a fixed-blade fan, surprisingly. Using a thermal clutch fan with a 24" 'big block' radiator and shroud will cure all cooling problems for your car - if it even has cooling problems.

Correct timing, 192 degree stock thermostat, shroud, and proper cooling fan are all very important.

I'm sorry to 'pick on you', @[email protected] ! I appreciate you being a part of these forums, and don't want to feel like I'm smacking you down either. A lot of people get a lot of misinformation about radiators and cooling, and I see an awful lot of people spending big bucks on stuff that doesn't work well.

Best wishes, you guys.

Awesome feedback Grimbrand - thank you. I am not sure a 24" big block radiator will fit... is this a conversion that you have taken on?
 

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I live near Victorville, CA, same desert as Phoenix.

The gauge can be calibrated. Put the temp sensor in boiling water, measure the resistance, substitute that resistance for the sensor, set the gauge to read boiling at a point of your choice: I set mine at the line at the end of the sweep, not full scale.

The referenced album records the three stages of radiators/fans in my 65.
 

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I bought my '69 302 powered convertible in 1998. The first problem I had to address was the overheating when in situations like restaurant drive throughs or in traffic after having been operating at speed. I installed a shroud, replaced the fan with a Flex-A-Lite, had the radiator recored with a 3 row (I didn't like the look of the aluminum top tanks), changed thermostats, replaced senders, used distilled water......no joy. Then I moved from the temperate Bay Area to the Sacramento area with 110* summer days. My eventual solution was an underdrive pulley on the water pump and another new thermostat, back to 180* from a 160*. Everything settled right down. Ford used those lousy two row 17" radiators on everything but the A/C and big block cars and they are worthless. Before my final solution I had pulled the radiator on the chance that it had become restricted. A local radiator shop did a flow check and let me watch. He said he had never seen a radiator that flowed as clean and as strong as mine. BTW, I am now running a 6 blade Ford fan. When I had the 302 short blocked years ago and reinstalled it myself, the machine shop wanted to see my install before they would warranty the engine. The only change they wanted was that I get rid of the Flex-A-Lite fan. They said it doesn't pull enough volume to effectively keep the engine cool at idle.
 

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1966 Mustang A-Code Coup, 289 V8 Automatic transmission
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Discussion Starter · #26 ·
I live near Victorville, CA, same desert as Phoenix.

The gauge can be calibrated. Put the temp sensor in boiling water, measure the resistance, substitute that resistance for the sensor, set the gauge to read boiling at a point of your choice: I set mine at the line at the end of the sweep, not full scale.

The referenced album records the three stages of radiators/fans in my 65.
Oh that’s awesome… how do I adjust the gauge? Is there an adjustment screw on it somewhere?
 

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Awesome feedback Grimbrand - thank you. I am not sure a 24" big block radiator will fit... is this a conversion that you have taken on?
It's not as easy with the early Mustangs; '67+ they just bolt right in. I have experience with that, in my '67 Cougar. I think the '64 1/2-66 mustangs have a narrower opening in the radiator support that requires some mods to put in a big-block radiator. I know guys do it, but I'm not sure about everything involved. I suppose if you're willing to cut the support, it's not that big of a deal; the radiator attaches top and bottom with brackets, and that part should be easy enough. The factory radiator is pretty good for a 289 or 302, but if you've got some big performance mods, or a 351, and especially if you have air conditioning too, it might be overwhelmed. The extra 6" of width on the big-block radiator do make a difference. It doesn't help that the shrouds on the early 'Stangs are absolute garbage too; more like a "don't put your fingers in here" thing than a ducted-fan setup.
 

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Patbuch, I hate to disagree with you here, but you want LESS rows with an aluminum radiator than brass - not more. This is very important. Usually 3 core brass or 2 core aluminum is the most you want. Aluminum radiator tubes are stiffer, and can be made wider than the softer copper tubes in a brass radiator. That means a 2 core aluminum is about the same thickness as a 3 core brass radiator.
So why not add more rows? Two big reasons. The first one's simple. Fitment. They get too thick, and it's hard to get them in there with a fan and shroud, unless you want to customize your radiator support and go through a lot of fuss. The other very good reason is that with extra fins and thickness, air trying to get through has more resistance. It's hard to force enough airflow through it. Worse, slow-moving air picks up a ton of heat from the first cores. When it's saturated with heat, the last rows of fins do nothing to cool the radiator any more than the smaller thinner radiator that lets air through more easily.
Aluminum radiators work well, and are lighter than brass, but aluminum also tries to work as a sacrificial anode to convert rust back to iron. If your car's block has significant corrosion inside, you will need to be sure to change out your antifreeze frequently (it has anti-corrosion agents that will break down over time). Failure to do so will mean your nice new aluminum radiator starts to be eaten away from the inside out, and it will spring leaks as it tries to 'fix' your block.
Always use only distilled water in your cooling system (along with good quality antifreeze) Tap water greatly accelerates corrosion.

And lastly, if you have a choice, never use a flex fan. The blade design is not very efficient. They thrash air around and typically steal even more power than a fixed-blade fan, surprisingly. Using a thermal clutch fan with a 24" 'big block' radiator and shroud will cure all cooling problems for your car - if it even has cooling problems.

Correct timing, 192 degree stock thermostat, shroud, and proper cooling fan are all very important.

I'm sorry to 'pick on you', @[email protected] ! I appreciate you being a part of these forums, and don't want to feel like I'm smacking you down either. A lot of people get a lot of misinformation about radiators and cooling, and I see an awful lot of people spending big bucks on stuff that doesn't work well.

Best wishes, you guys.
Thx for that info....im never too old to learn new things
 

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I learned from having similar heating "issues" that replacing the radiator cap was all that was needed...after MONTHS of doing what you're doing. If your new prize had been sitting for a long time, yours may have gotten weak, too. It seems without adequate pressure caused by the cap, adequate fluid was never circulating to the rear of the block, thus that was getting really hot and eventually radiating toward the rest of the engine and causing problems after enough time lapsed. Give it a try and (hopefully) save yourself a lot of angst and dollars.
 

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1966 Mustang A-Code Coup, 289 V8 Automatic transmission
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Discussion Starter · #30 ·
Hey all - so my son and I have been (slowly) working through this overheating issue and collecting data. We went through the temperature readings with an IR gun again and this time I found very clearly that the gauge was pegged when the temperature upstream of the thermostat was only 180 degrees. So I think I have a sending unit problem. Here is the rub, though...at some point, someone installed a sensor with a 1/8" npt body, and a 1/8 to 1/4 brass bushing. Now the bushing is stuck in the hole, and I can't get it out. I could probably mangle the thing to get it out, but I am a little concerned about why someone did this in the first place, and think I might be opening another can of worms... My preference is to find a sending unit with 1/8 NPT threads that will allow m gauge to read properly. From what I can tell, I need it to have about 10 ohms of resistance at 200 degrees. But I cant seem to find any publication that tells me sending unit ohms vs temperature for a catalog of sending units.

Can anyone point me to some sending unit OHM data?
Alternatively, does anyone know of a 1/8 NPT sending unit that will work with my 66 Mustang 289 gauge?

Eye Automotive tire Human body Wood Eyelash
 

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You can buy a 64.5 -65 temp sender that should fit straight into that bush.
There are 2 different sizes between 64.5 and 66.
Pre 9/1/65 had a smaller thread and after 9/1/65 had a larger thread size.

Is that manifold correct to your car?
 

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1966 Mustang A-Code Coup, 289 V8 Automatic transmission
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Discussion Starter · #32 ·
Ok thanks - I looked at one of these from CJ Pony and they said the pre-9/1965 model was for a light, not a gauge… so I think the resistance goes to zero at about 210-ish degrees. Do I have that right? Did the 64.5 model have a light?

I am not following your question on the manifold…
 

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All models have a temp gauge.
I was referring to your inlet manifold, has it been swapped out for an after market one?
Regardless if it is a pre or post 65, both styles will work with each other if you use the adapter bushing like you have in the above picture.
 

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Discussion Starter · #34 ·
Ahhh - ok. Nope - as far as I can tell it is all original. I will try the pre-9/65 sending unit.
 
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